1. Field of the Invention
This invention relates in general to the field of wavelength division multiplexing and more particularly to a multifunctional and reconfigurable Dense Wavelength Division Multiplexing (DWDM) optical node. This invention also relates to an optical node and an optical network including a reconfigurable optical add drop multiplexer core device.
2. Description of Related Art
Wavelength Division Multiplexing (WDM) and Dense Wavelength Division Multiplexing (DWDM) are technologies that enable a multitude of optical wavelengths of differing frequencies to be transported over a single optical fiber. A DWDM network is constructed by interconnecting multiple DWDM network elements. Each network element typically includes, for example, optical multiplexing equipment, optical de-multiplexing equipment, optical amplifiers, optical power monitors, optical supervisory channel processors, network element control processors, and optical converters.
First generation DWDM network equipment provided the ability to transport a multitude of optical wavelengths between two points over a single pair of optical fibers. These systems are referred to as DWDM point-to-point systems. Second generation DWDM network equipment provided the ability to interconnect DWDM network elements in a “ring” configuration. These elements included two DWDM network interfaces and multiple single wavelength ports used to add and drop wavelengths to and from the DWDM network interfaces. Second generation DWDM network elements provided the ability to “pass” wavelengths directly between their two DWDM network interfaces. However, in order to do this, fiber cables had to be manually interconnected within a system each time a “pass-through” connection was required.
Third generation DWDM network elements included Reconfigurable Optical Add Drop Multiplexers, referred to as ROADMs. ROADMs provided the ability to remotely reconfigure the DWDM network element. For these systems, wavelengths could be remotely configured to pass through the network element without manual intervention. Since these “third generation” DWDM network elements also included only two DWDM network interfaces, they are referred to as 2-degree network elements. But these “third generation” DWDM network elements connect only a single add-on device to the ROADMs. As a result, while they are reconfigurable, they are not multifunctional, which limits their usefulness.
Thus, it is useful to have a fourth generation DWDM optical node that is a multifunctional in addition to being reconfigurable. In addition, it is useful to have a multifunctional and reconfigurable DWDM node employing a ROADM connected to more than one add-on device to provide multifunctionality. Further, it is useful to have an optical network including a plurality of such optical nodes.